Circuit for starting and operating gaseous discharge devices



April 22, 1958 FElNBERG 2,832,008

CIRCUIT FOR STARTING AND OPERATING GASEOUS DISCHARGE DEVICES OriginalFiled May 17, 1951 IN V EN TOR.

Albert E Feinber BY United States Patent CIRCUIT FOR STARTING ANDOPERATING GASEOUS DISCHARGE DEVICES Albert E. Feinberg, Chicago, Ill.,assignor to Advance Transformer Co., Chicago, Ill., a corporation ofIllinois 9 Claims. or. 315-438) This application is a division of myapplication Serial No. 226,820, filed May 17, 1951, now Patent2,813,228, which was co-pending with and is a continuation in part ofapplication Serial No. 135,669, filed December 29, l949, and issued June26, 1951, as Patent No. 2,558,293, and relates to circuits for gaseousdischarge lamps.

It is one of the objects of the present invention to provide a highlyefiicient circuit for initiating the discharge of a plurality of gaseousdischarge devices, which circuit and the apparatus required thereforwill be extremely simple and economical of contraction and operatron.

in connection with the above object it is pointed out that my newinvention utilizes a simple three winding transformer, the generalconstruction ofwhich is similar to that type of transformer used incircuits for starting preheated filament fluorescent lamps.Specifically, no special cores are required, no ChOlEfiS or inductancesneed be used in the circuit, and one relatively cheap condenser may beused. The invention lies in the connections of the circuit, the mannerof forming and the proportions of the windings, as well as other factorsto be pointed out which give rise to the advantages of my invention.

It is a further object or" the present invention to provide a circuitfor initiating the discharge of a pair of instant start gaseousdischarge devices seriatim and thereafter providing goodregulation forthe llow of current therethrough. It is a still further object of thepresent invention to provide a circuitfor initiating the discharge of apair of gaseous discharge devices in which following the initiation ofthe discharge and during operation of the devices the devices are ineffect connected in substantially a series circuit. It is a furtherobject of the present invention to provide a circuit of the abovementioned character which may be used for initiating the discharge of asingle instant start gaseous discharge device.

it is a still further object of the present invention to provide acircuit for one or more gaseous discharge devices which will utilize asimple transformer for the purpose of providing the necessary startingvoltage and regulating inductance. present invention to provide acircuit for one or more gaseous discharge devices that utilize a highleakage reactance winding that facilitates the building up of thenecessary ignition voltage but which after ignition is so arranged inthe circuit that very little current passes therethrough, wherebytheremainder of the circuit including the gaseous discharge device ordevices constitutes in effect a series circuit substantially by-passingthe high leakage reactance winding. It is a still further object of thepresent invention to provide a circuit for one or more gaseous dischargedevices wherein a capacity reactance is associated with a high leakagereactance winding in such a manner as to build up a voltage across thereactor during starting, which will be of reverse relationship to thenormal direction of voltagein said high leakage tea-c It is a stillfurther object of the I Patented Apr. '22, 1958 ance winding, wherebythe voltage will be added to other voltages of the apparatus to igniteone or more of the gaseous discharge devices.

The attainment of the above and further objects of the present inventionwill be apparent from the following specification taken in conjunctionwith the accompanying drawings forming a part thereof.

In the drawings:

Figure l is a schematic electrical diagram showing one circuit embodyingthe present invention;

Figure 2 is a side elevational View of a transformer of the circuit ofFigure 1;

Figure 3 is a view similar to that of Figure 2 but showing a modifiedform of transformer; and i Figures4, 5 and 6 are schematic electricaldiagrams showing modified forms of circuits embodying the presentinvention.

Reference may now be had more particularly to the drawings wherein likereference numerals designate like parts throughout.

In the drawings, 10 designates generally a transformer which forms animportant part of my apparatus. The same is formed of threeindependently formed windings 11, 12, and 13 comprising a primary (P),first secondary (S and second secondary (S respectively.- All of thewindings are mounted upon a central winding leg M which is pressed intoan elongate shell 15, there being a magnetic shunt l6 and an air gap 17between the windings 11 and 12. The shell 15 and the winding leg 14 areformed of electrical steel laininations in the usual manner, therebyproviding an iron core for the transformer 10. i i I The windings aremounted upon the shell 15 in a manner such that the primary 11 is in thecenter of the shell 15, the second secondary 13 is on the left end ofthe shell 15 although mounted on the central winding leg rams the firstsecondary 12 is on the right.

end of the shell 15, separated from the winding 11 by the magnetic shunt16, and thereby constituting the winding 12 a high leakage reactance. Itis obvious that the windings 12 and 13 are'both loosely coupled with theprimary 1]., but that the first secondary 12 is what may be termed veryloosely" coupled to the primary, when comparing it with the secondsecondary coupling.

Although both coils l2 and 13 have high leakage reactance, it may beadvisable under certain operating conditions to place a small magneticshunt 16 and a gap 17' between coils 11 and 13 to provide additionalleakage reactance as shown in transformer 10 (Fig. 3).

The windings 11 and 12, namely the primary P and the first secondary Sare woundin the same direction to provide additive voltage, while thewinding 13 comprising the second secondary S is Wound in an oppositedirection to provide bucking voltage.

Referring to Fig. 1, note that the windings 11, 12, and 13 are connectedin series providing junctures 20 and 21 therebetween, the right hand endof the transformer 10 being designated 22. and comprising the free endof the winding 13 while the left hand end of the transformer beingdesignated 23 and comprising the free end of the winding 11. Note thatthe windings are not mountedin the order in which they are connected.

There are shown two gaseous discharge devices, comprising a firstfluorescent lamp 24 and a second fluorescent lamp 125. My apparatusincludes a condenser 26 in'a load connecting lead 27 which is connectedto the juncture 21. The lamp 24 is arranged in series withthe condenser26, having aload connecting lead 27' from the condenser 26 connected toits right handside, while the left hand side of the lamp 24 is connectedvia a load connecting lead 28 to juncture 23. Thus, it will appear thatthe first lamp 24 is connected across the primary and first secondary ofthe transformer 10, and in series with the condenser 26. The secondfluorescent lamp 25 has its right hand end connected by the lead 29 tothe terminal 22, and its left hand end by lead 3% to the juncture 21).Thus it will be obvious that the second lamp is connected across thefirst and second secondaries. The very loosely coupled secondary 12 iscommon to the circuits of both lamps 24 and 25. The usual A. C. line 31is connected across the primary 11 to provide the necessary power.

The first secondary winding 12 has sufiicieut turns so that it steps upthe line voltage of tie primary 11 considerably, in some instancesalmost four times. This voltage E is additive to the line voltage orprimary voltage E and since windings 11 and 12 are in series and acrosslamp 24, they add to provide igniting voltage for the lamp 24. Althoughthe winding 13 is so constituted that it provides an induced voltage Eof more than twice E since its voltage is in opposed relationship tovoltage of S the voltage across lamp 25, which is the vector sum of Eand E will be very little prior to any current flow, and certainly lessthan required to ignite the lamp 25.

The voltage across condenser 26 is negligible prior to ignition of lamp24, and hence the voltage E combined with E appears across lamp 24,lights the lamp, and causes current to commence flowing.

Current now flows in the circuit of lamp 2d, and since the inductiveractance of the very loosely coupled secondary S is so great compared tothe capacitive react ance of the condenser 26, the current of suchcircuit is lagging. The condenser 26 assists in shiftin the phase of thevoltage in the first secondary 12 by lowering the total reactance of thecircuit of lamp 2d. Such effect causes a higher flow of current and aconsequently greater induced voltage across S which, of course, aids incans ing lamp 25 to ignite.

I have found that the current flow caused by the ignition of the firstlamp 24 gives rise to voltage in the winding 12 whose phase is in efiectreversed relative to the phase of voltage E and hence is additiverelative to voltage E of windings 13, which is the secondary Thisvoltage is of such magnitude that the combined voltage appearing acrosslamp 25 is sufiicient to ignite the lamp and cause flow of currenterethrough.

With current flowing through both lamps 24 and 25, the high inductivereactance of winding 12 serves to resist flow of current therethroughand thus the effective circuit is a series circuit with both lamps 24and 25 which may be traced as follows: luncture 23, lead 28, lamp 24-,lead 27 and condenser 26, juncture 21, winding 13, terminal 22, lead 29,lamp 35, lead 30, juncture 20. The wind ing 12 is thus not an effectivepart of the operating circuit. The leading current of the secondary S,caused by condenser 26, and the lagging magnetizing current of theprimary may so neutralize their respective effects that the power factorof current drawn from the line leads 31 is almost unity. It is obviousthat the lead 28 and the left hand one of the line leads 31 mayconstitute a single lead and that the lead 31 and the right hand one ofthe line leads 31 may also constitute a single lead.

In the event the current drawn from the line is lead ing, an additionalgap 40 may be formed at the end of the winding leg 14 thereby increasingthe leakage reactance of the apparatus while incidentally preventingsaturation of the core from too greatly distorting the wave shape.

An example of apparatus embodying my invention readily could beconstructed for initiating the discharge and providing regulation from apair of fluorescent lamps known commercially as T-12 lamps having aneffective length of 48 inches and being rated at forty watts each. Suchapparatus has been successfully produced and operated. The laminationsof the shell of the transformer had the dimensions of approximately twoand one-eighth by five and one-quarter inches, and the stack thicknesswas approximately one inch. The magnetic shunt may be approximatelyone-half inch wide, and the gap 17 approximately .0l0 inch. The windowsfor the windings 11, 12, and 13 may be adjusted in size in accordancewith the physical volume of the windings.

The primary winding 11 was formed of 540 turns of number wire; the firstsecondary winding 12 was formed of 2360 turns of number wire; and thesecond secondary winding 13 was formed of 1270 turns of number 27 wire.The condenser 26 had a capacity of 2.6 microfarads and a rating of 440volts maximum voltage. This apparatus operated in a highly satisfactorymanner and the lamps 24 and 25 were ignited with such speed that italmost appeared that they ignited simultaneous- 1y when the power wasturned on.

With -a 118 volt cycle A. C. line connected across the primary 11, thevoltage E was 405 volts, and the voltage E was 270 volts. E and E (theline or primary voltage) are additive because the windings 11 and 12 areformed in the same wound direction. E on the other hand is a buckingvoltage because the winding 13 is formed in the reverse manner. Thesevoltages exist before the lamps 24 and 25 are ignited. Measurementstaken across the various windings bear this out in the following manner:The voltage measured from juncture 23 to juncture 21 was found to be 520volts; the voltage measured from juncture 20 to terminal 22 (across bothsecondaries 12 and 13) was found to be 150 volts; and the total sum or"voltages across the entire transformer 10 taken from juncture 23 to 22was found to be 270 volts. Since the type of lamp in the circuitrequires approximately 450 volts to ignite, obviously the first lamp 24will ignite since it has almost 520 volts appearing across itsterminals, while the second lamp 25 will not ignite because the totalvoltage across it is only approximately 150 volts. These measurementsmay be taken by removing the lamps 24 and 25 from the circuit.

Once the lamp 24 has ignited and the gas therein has broken down,current flows through that lamp, said current being limited by thereactance of the circuit including the high leakage reactance of thesecondary 12.

With the lamp 24 operating, measurements can be taken of the voltagesand currents in the apparatus while the lamp 25 is omitted, and suchmeasurements are as follows: E is now only 210 volts and E appears to be258 volts, while E remains at 118 volts; the voltage measured fromjuncture 23 to juncture 21 is now 162 volts indicating a radical changewhich I believe is caused by a phase shift having the eifect ofproviding a voltage vector component additive to the voltage across Sthe secondary winding 13, and bucking the voltage E across the primaryP; the voltage across the lamp 25 measured from juncture point 20 to 22is now 440 volts, 'or sufiicient to ignite the lamp 25; the voltageacross the entire transformer 10 from juncture 23 to 22 is 315 volts;the voltage at the terminals of the lamp 24 is 140 volts and that acrossthe condenser 26 is volts; the current in the primary 11 is found to be.8 ampere and the current in the lamp 24 is found to be .120 ampere.

The above measurements are static, that is, made with only the lamp 24operating and the lamp 25 not in the circuit. This situation will ariseif the lamp 25 burns out, and it will be obvious from the values giventhat the apparatus is operating satisfactorily and may continue to doso, providing an important emergency feature for my apparatus.

It is probable that the initial surge of current occurring with ignitionof lamp 24 will produce voltages in the first secondary l2 and thesecond secondary 13 whose sum will be considerably greater than 440volts, but in any event, even this sum static voltage is suflicient toignite lamp 25 when in place.

After lamp 25 has also become ignited, current flows in its circuit, andthe condition of voltages and currents in the apparatus as determinedbymeasurements is as follows: The primary voltage E is still 118 volts;the voltage across S the first secondary winding 12 is 310 volts; acrossthe second secondary S the voltage is 308 volts; the voltagemeasuredfrom juncture 23 to juncture 21 is 415 volts; the voltage acrossthe second lamp 25 from juncture to 22 is 107 volts; the voltagemeasured across the entire transformer 10 from juncture 23 to 22 is 130volts; the voltage across the lamp 24 at its terminals is 107 volts; thecondenser voltage is 418 volts; the current flowing in each lamp isapproximately .435 ampere; and the current in the primary 11 is found tobe .580 ampere. With both lamps 24 and 25 operating the current measuredin secondary S is only .030 ampere, which demonstrates that the highreactance of the winding 12 has the effect of forcing the entire circuitto act as a series arrangement so that the major flow of current isthrough the lamps 24 and 25, the winding 13, and the condenser 26. Withsuch a circuit, the reactance occasioned by the presence of thecondenser 26 is effective to counterbalance the inductive reactance ofthe transformer primary, so that there is very good power factorcorrection and the current drawn from the line 31' can be adjustedpractically to be almost in phase with the line voltage.

It should be obvious that for different types of lamps the circuitconstants of my apparatus can be adjusted.

The circuit of Fig. 4 is essentially the circuit of Fig. 1 except thatthe lamp 24 of Fig. 1 has been omitted and the condenser 26 isconnected'directly across the terminals 2123. It is believed that theoperation of this circuit will be apparent from the description abovegiven 1.

of the operation of the circuit of Fig. 1. I

In Fig. 5 there is shown a circuit, substantially that of Fig. 4 exceptthat there has been added an iron core choke 80 to improve the waveshape of the currents supplied to the lamp 25. The power factor of theapparatus as described will be capacitive, the lamp 25 drawing a leadingcurrent, since the impedance of the condenser 26 is greater than theimpedance of the secondary S This leading power factor could becorrected by increasing the magnetizing current in the primary (P). Incertain cases this can be done by varying the number of turns and thephysical constants of the apparatus. An increase of the magnetizingcurrent in the primary can be obtained by decreasing the number ofprimary turns or increasing the width of the end air gap 40 in the caseof the core of Fig. 3. While the core structure of Fig. 2 does not havean end air gap such as the gap 40, this may be provided if desired. Twodifliculties arise if an attempt is made to increase the primarymagnetizing current by decreasing the number of primary turns orincreasing the width of the air gap 40. In the case of increasing thewidth of the end air gap, less flux will link with the secondary S sincesuch flux is being forced through other leakage and shunt paths, as isillustrated with reference to the core shown in Fig. 3. Increasing thewidth of the gap 40 increases its magnetic reluctance and thereby forcesmore flux to go through the shunt 16'.

The addition of the choke 80 operating below saturation introducessufiicient inductance reactance without upsetting the characteristics ofthe apparatus, so that the wave shape is improved and greater lightingefiiciency is achieved. It permits reduction in the size of the wire inthe secondary S since the current therein isreduced. The saving incopper in the winding S partially offsets the cost of the additionalchoke 80. In the circuit of Fig. 4 the choice may be separate from thetransformer or it may be embodied in a combined structure therewith, asshown in my application Serial No. 182,212 filed August 30, 1950,entitled, Magnetic Apparatus for Gaseous Discharge Circuits.

Still another embodiment of'the present invention is illustrated in thecircuit of Fig. 6. Here the condenser 26 is connected across the primaryand the secondary 6 S as in the circuits of Figs. 4' and 5. The lamp .25is connected across all three of the transformer windings. The secondarywindings S and S, are in opposition.

In the circuit of Fig. 6, current is first developed in the circuitincluding the condenser 26 connected across the primary and thesecondary S The voltage across the secondary S under open circuitconditions, that is, with the lamp 25 omitted and the condenser 26 opencircuited, is greater than the line voltage. Before current commences toflow in the secondary S the voltage across all three coils isinsuflicient to ignite the lamp 25. However, after current commencesto'fiow through the condenser and the primary and secondary S thereverse phase current in the secondary S combines with the voltage inthe secondary'S and the vector sum of the voltage across all thewindings is sufiicient to ignite the lamp 25, after which the deviceacts asa straight transformer.

In the above described apparatus, while I have referred to the use of aseparate choke, I do not require such an element as a part of theinvention. I believe that the use of my apparatus in connection withsuch a choke is an improved version of that which I consider the basicnovelty. In some cases the use of a choke may give more satisfactoryresults, but the manner of operation and construction of the apparatusis not essentially altered by the addition.

It is also desired to point out that the two windings P and 5;, arerelatively closer coupled together than the winding S is to either. Thewinding S must in all cases have a large leakage reactance in order togive the desired results, and hence it is preferably placed on the endof the transformer core. There is a magnetic shunt between it and theremainder of the transformer. As the number of turns of S increases theshunt may be made smaller in width and conceivably may be dispensed withdue to the high inductance provided by a great many turns. As for theother two windings, they can physically be interchanged as to position,and may even be wound on top of one another with the addition of somemeans providing ,a lagging reactance to supply that which is eliminatedby this expedient. In the circuit of Fig. 5, for example, the windings Pand S; can

be wound one on top of the other, giving excellent results, and a chokesupplies the lagging reactance needed for good regulation.

A few additional examples of the constants of the transformers used inconnection with the circuits shown in. Figs. 4, 5 and 6 are given below.In each case each lamination of the transformer was of electrical steel2.125 by 5.25 inches, the framing portion being generally inch wide'allaround, and the central winding leg being 4; inch wide. One constructionof the transformer was as follows:

Example 1.(Transformer of 3 Stack height inch Primary winding P-590turns of No. 26 wire Secondary winding S 2000 to 2200 turns of No. 32wire Secondary winding S -930 turns of No. 28 wire Gap 40.016 inch I Gap17'.015 inch Gap 17-.0l0 inch Shunt 16 /4 inch Shunt 16% inch Capacitor75-3 /2 mfds., 400 v. A. C. R. M. S.

7 Example 2.--(Transformer Fig. 3)

Stack height-+1 inch Primary winding P6l0 turns of No. 26 wire Secondarywinding S -22l0 turns of No. 35 wire Secondary winding S 820 turns ofNo. 27 wire Gap 17-.015 inch Shunt 16 /s inch Capacitor 26-275 mfd. 400v. A. C. R. M. S. Choke 80 (where used)- /s inch square El stack oflaminations inch thick having 1000 turns of No. 29 wire On a 115 volt A.C. line, a 48" T-lZ 40 watt instant start fluorescent lamp was ignitedand satisfactorily opcrated. In the case a choke was not used, an endgap of approximately .015 inch was used. The open circuit voltage acrossthe lamp was approximately 430 volts. The current in S during startingwas .200 ampere and after starting it was .050 ampere. The total currentdrawn during operation was .600 ampere and the voltage across the lampwas approximately 110 volts. The current in the secondary S duringoperation was .46 ampere. During starting the current in the primary(drawn from line) was 1.1 amperes.

Although the examples which have been illustrated and described show thethree windings P, S and S connected respectively in series, it will beobvious to one skilled in the art, after becoming cognizant of theteachings hereof, that the invention can be applied with substantiallythe same effect in case the windings are connected in a different order.Thus, for example, the primary may be connected between the twosecondaries, or the secondaries as illustrated and described may beinterchanged as to electrical position. By adjustment of the physicalcon stants, the results described herein and the advantages derived fromthe invention can be secured.

In compliance with the requirements or" the patent statutes I have hereshown and described a few preferred embodiments of my invention. It is,however, to be understood that the invention is not limited to theprecise constructions here shown, the same beinc merely illustrative ofthe principles of the invention.

What I consider new and desire to secure by Letters Patent is:

1. Lighting apparatus comprising, in combination, a pair of positivecolumn type gaseous discharge lighting devices, an alternating currentsupply for the devices comprising a three-winding auto-transformerhaving a primary, a loosely coupled first secondary having one end rconnected with the said primary, a loosely coupled second secondary, thesaid first secondary having its second end connected with the secondsecondary and in bucking voltage relationship to the second secondary,means including a capacitive reactor connecting one of said devicesacross the primary and the first secondary, means connecting the secondof said devices across the first and second secondaries, and thereactance of the first secondary being very high relative to the secondsecondary whereby after the said devices are both operating theapparatus will form in effect a series circuit connected across theprimary, said circuit including the devices, the capacitive reactor, andthe second secondary.

2. Lighting apparatus comprising, in combination with two positivecolumn type gaseous discharge lighting devices, an auto-transformerhaving a primary, a loosely coupled high leakage reactance firstsecondary of more turns than the primary and connected in step-upautotransformer relationship with the primary, and a second looselycoupled high leakage reactance secondary of more turns than the primarybut arranged in bucking relation thereto, said primary and said firstsecondary and said second secondary being connected one after the other,means including a capacity reactor connecting one of said devices acrossthe primary and only the first of the two secondaries, and meansconnecting the second of said devices across the two secondaries.

3. Lighting apparatus comprising, in combination with two positivecolumn type gaseous discharge lighting devices, means for operating thedevices from a source of alternating current whose voltage issubstantially less than the starting voltage of either of the devices,said means including reactive means having a primary winding and firstand second secondary windings loosely coupled to the primary and to oneanother, the coupling of the first secondary winding being substantiallylooser relative to the other two windings whereby to constitute same ahigh leakage reactance winding, the windings being connected one afterthe other with the first secondary winding connected between the othertwo windings, and the second secondary winding being connected inbucking voltage relationship to the'other two windings, a capacitivereactor having one side thereof connected to the common juncture of thesecondaries, means connecting the first of said discharge devicesbetween the second side of the capacitive reactor and that end of theprimary winding which is remote from the first secondary and meansconnecting the second of said discharge devices across both secondaries.

4. An operating circuit for two positive column type discharge devices,comprising a transformer having a primary, a first secondary and asecond secondary, a first positive column type gas discharge deviceconnected in a loop with the two secondaries and the voltages of saidsecondaries in opposition to one another in said loop prior to the flowof current through the secondaries whereby at that time their efiectivevoltage is a function of the difference between the voltages across thetwo secondaries, a second positive column type gas discharge deviceconnected across at least a major portion of the primary and the firstbut not the second of the two secondaries, the first secondary being instep-up auto-transformer relationship to the primary, a magneticstructure coupling the primary with the two secondaries, the secondariesbeing more closely coupled to the primary than to one another, saidfirst secondary taking a lagging current upon starting of current flowtherethrough whereby after current commences to flow therethrough thedirection of the voltage across the first secondary is substantiallyreversed with respect to the voltage induced in the other secondary andthe voltage across the device in said first loop becomes a function ofthe sum of the voltages across the two secondaries, said first secondarybeing of substantially higher reactance than that of the othersecondary, and a condenser in series with the first secondary and of acapacity reactance less than the inductive reactance of the firstsecondary.

5. A lighting system comprising a transformer having a primary, a firstsecondary, a second secondary, an instant start positive column typedischarge lamp connected in a loop with the two secondaries and thevoltages of said secondaries in opposition to one another in Said loopprior to the flow of current through the secondaries whereby at thattime their effective voltage is a function of the difference between thevoltages across the two secondaries, a load including a condenserconnected across at least a major portion of the primary and the firstbut not the second of the two secondaries, the first secondary being instep-up auto-transformer relationship to the primary, a magneticstructure coupling the primary with the two secondaries, said structureincluding a rectangular shell and a central winding leg between thetransverse ends of the shell, the secondaries being at the ends of thecentral leg and the primary being between the secondaries so that thesecondaries are more closely coupled to the primary than to one another,magnetic shunts bridging a major portion of the space from the centralleg to the shell to provide high leakage reactance for the secondaries,said first secondary taking a lagging current upon starting of thecurrent flow therethrough whereby after current commences to flowtherethrough the direction of its induced voltage is substantiallyreversed with respect to the voltage induced in the other secondary andthe voltage across said lamp becomes substantially a function of the sumof the voltages across the two secondaries, said'first secondary beingof substantially higher reactance than the other secondary, and meansfor preventing saturation of the central core leg adjacent the secondsecondary, comprising a bridged air gap between the adjacent end of thecore leg and the shell.

6. A system comprising two positive column type instant start gaseousdischarge devices, an auto-transformer supplying alternating currentthereto said transformer having a primary, a loosely coupled firstsecondary having one side connected to one side of said primary and inadditive voltage relationship thereto, and a loosely coupled secondsecondary having one side connected to the second side of said firstsecondary and in voltage bucking relationship to said primary, acapacitive reactor, one of said devices being connected across theprimary and the first secondary and in series with the capacitivereactor, the second of said devices being connected across the twosecondaries.

7. A lighting system, at least two positive column type instant startgaseous discharge devices, means for operating the devices from a sourcehaving a voltage substantially lower than the igniting voltage ofeitherof said devices, said means comprising an auto-transformer havinga primary, a first secondary, anda second secondary connected one afterthe other, one of the devices being connected across the primary and onesecondary together, the other of said devices being connected across thesecondaries together and with the secondaries in voltage opposition toone another, the primary and first secondary being in step-upauto-transformer relationship to provide a voltage for igniting said oneof saiddevices, and the combined voltages of the secondaries beingsutficient for igniting the other device but the secondaries beinginductively arranged additively to combine their voltages only afterignition of said one device, and means comprising a magnetic shuntestablishing a high leakage reactance in, said first secondary toprevent substantial passage of current therethro'ugh after ignition ofboth devices.

8. An operating circuit for two discharge devices, comprising atransformer having a primary, a first secondary and a second secondary,a first gas discharge device connected in a loop with the twosecondaries and the voltages of said secondaries in opposition to oneanother in said loop prior to the flow of current through thesecondaries whereby at that time their etfective voltage is a functionof the difiFerence between the voltages across the two secondaries, asecond gas discharge device connected across at least a major portion ofthe primary and the first but not the second of the two secondaries, thefirst secondary being in step up auto-transformer rela-' tionship to theprimary, a magnetic structure coupling the primary with the twosecondaries, the secondaries being more closely coupled to the primarythan to one another, said first secondary taking a lagging current uponstarting of current flow therethrough whereby after current commences toflow therethrough the direction of the voltage across the firstsecondary is substantially reversed with respect to the voltage inducedin the other secondary and the voltage across the device in said firstloop becomes a function of the sum of the voltages across the twosecondaries, saidfirst secondary being of substantially higher reactancethan that of the other secondary.

9. A lighting system comprising two instant start gaseous dischargedevices, an auto-transformer having a primary, a loosely coupled firstsecondary having one side connected to one side of said primary and inadditive voltage relationship thereto, and a loosely coupled secondsecondary having one side connected to the second side of said firstsecondary and in voltage bucking relationship to said primary, acapacitive reactor, one of said devices being connected across theprimary and the first secondary and in series with the capacity reactor,the second of said devices being connected across the first and secondsecondaries, the second secondary being of lower reactance than thefirst secondary and being more closely coupled to the primary than isthe first secondary.

References Cited in the file of this patent UNITED STATES PATENTS2,269,978 Kronmiller Jan. 13, 1942 2,382,638 Keiser Aug. 14, 19452,558,293 Feinberg June 26, 1951

